Fuze for spin stabilized projectiles



Jan. 30, 1968 M. L. MYERS ET AL 3,366,059

FUZE FOR SPIN STABILIZED PROJECTILES Filed Jan. 9, 1967 2 Sheets-Sheet l VII | l 2 l9 5 IO INVENTORS.

.- MARTIN L. MYERS BY JOHN v. MURPHY Maw ATTORNEY Jan. 30, 1968 M. L. MYERS ET AL 3,366,059

FUZE FOR SPIN STABILIZED PRQJEGTILES I Filed Jan. 9, 1967 2 Shets-Sheet 2 INVENTORS. MARTIN L. MYERS Z JOHN v. MURPHY ATTORNEY United States Patent Ofiice 3,3tfi,@59 Patented Jan. 30, 1968 ABSTRACT UP THE DISCLUSURE In a fuze having a spin axis a spherical rotor is mounted in floating fashion. A lead or part of a firing train is disposed in an axial channel in the rotor. A housing provides a generally spherical chamber in which the rotor floats. Bearings are carried by the rotor at the ends of a geometrical axis which is normal to the channel and normally angularly offset both longitudinally and laterally from an axial reference line through the center of the projectile. Raceways are formed on the housing to guide the bearings spirally as the rotor including the bearings is driven into a symmetrical configuration referencing the axis of rotation. The bearings turn the rotor to align the rotor axial channel with the spin axis and to arm the fuze. Another feature of the disclosure is the placement of an initiator in relation to and near the nose of a projectile in such manner that, whether on graze or high impact, firing is quickly initiated by a pinch effect eliminating all movable parts, and their resulting delays from the initiator.

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The present invention provides an improvement in fuses for spin stabilized projectiles.

The primary object of the invention is to provide a fuze construction in which the rotor is substantially balanced at all times and in which the firing train components within the rotor are located along a central axis of the rotor.

A further object of the invention is to provide, in a fuze, the improvement which comprises the combination of a spherical rotor having formed therein a channel which defines a rotor axis, a split housing adapted to house said rotor but to permit relative motion of the rotor, said housing defining a spin axis about which the split housing spins, diametrically opposed bearings seated on the periphery of the rotor and responsive to centrifugal force to be urged radially outwardly, said housing having spiral raceways individual to said bearings and so formed that angular deceleration of the housing and the centrifugal forces cause the bearings to be displaced to turn the rotor and to align the rotor axis with the spin axis, thereby arming the fuze.

Other objects of the invention are to provide a fuze characterized by an extended range of arming times, by ready adaptability to use with a variety of projectiles, and by particularly fast initiation of small-caliber highvelocity projectiles.

Other objects of the invention are to provide a fuze which will tolerate rough handling and reliably initiate firing on target impact.

A further object of the invention is to provide a mechanical fuze of reduced size and complexity.

The background of the invention Prior art spin stabilized fuzes of the ball-rotor type are subject to serious limitations in that they normally provide relatively short arming times and are limited to utility with specific projectile types.

Projectile velocity in firing with small-caliber shaped charge ammunition has heretofore been restricted by the long delay times of to 200 microseconds required for initiation of firing. The present invention not only permits extension of the arming time but it assures reliable quick-action firing of higher velocity projectiles.

In the conventional prior art fuze the rotor may be mounted for rotation on an axis of rotation which is transverse to the body of the fuze. Since the fuze spins as it passes through a gun, the spin causes a net moment tending to turn the rotor, unless the rotor is symmetrical and balanced relative to the axis. Therefore a balanced symmetrical rotor, if mounted on such an axis and initially set in an unarmed position, with its part of the firing train or lead simply turned at an angle with respect to the remainder of the firing train, would not be caused to turn and it would remain in the unarmed position. This is the reason why prior art rotors may be unbalanced and the firing train elements carried thereby may be offset with respect to the axis on which the rotor is mounted, in such manner that the forces generated by spin line up the firing train. It will be observed that arming is accomplished, in rotors of this type, at the price of unbalance. Now the present invention minimizes this ofiset and the resultant unbalance.

In prior art fuzes difiiculty has been experienced in quick initiation at graze angles of impact and the present invention provides an improvement whereby firing is quickly initiated either on graze impact or high impact.

The drawings For a better understanding of the invention, together with further objects, advantages and capabilities thereof, reference is made to the following description of the appended drawings, in which:

FIG. 1 is a sectional view as taken through the axis of a fuze in accordance with the invention, showing the fuze installed in the nose of a projectile, the fuze being in unarmed condition;

FIG. 2 is a section, similarly taken through the central axis of the fuze, showing it in armed condition;

FIG. 3 is a sectional view taken on line 3-3 of FIG. 2 and looking in the direction of the arrows, showing the locking pins 31 and 32 in the release position;

FIG. 4 is an axial sectional view showing the initiator portions of the fuze;

FIG. 5 is a front view of a projectile including a fuze in accordance with the invention, the ogive and upper fuze body being removed from the assembly so that the upper fuze body may be separately shown in the figure; and

FIG. 6 is a three-dimensional geometrical figure used as an aid in explaining the operation of the invention.

Initiating system Referring first to FIGS. 1 and 4, the details of the explosive initiating system are there shown. Reference numeral 10 designates a conventional ogive which is screwed onto the lower fuze body 11 by screw threads 12. The ogive has an annular groove providing an annular shoulder 13 against which the frontal margin of the lower fuze body abuts. The ogive defines a chamber 14 within which is disposed an initiator cover 1'5, the latter being of truncated conical configuration but being hollow and open at 16. Coaxially located within the cover 15 is an initiator housing 17 which is generally in the form of a truncated conical solid. This initiator housing is an internal former and the cover 15 is form sustaining for the This explosive initiating system offers the following advances in the state of the art:

First, the initiating time for high-velocity, small-caliber projectiles is reduced to a minimum.

Second, the initiating system has no moving parts, thereby insuring a high degree of reliability.

Third, the initiating system is simple and contains a small number of parts.

The ogive and initiator are designed to provide military safety based on their structural strength, as confirmed by rough handling tests.

The projectile upon impact will crush the ogive and pinch the initiator 21 between the initiator cover 15 and a manner to provide graze sensitivity of the fuze. The pinch effect detonates the initiator 21. The lead 24 in the ball rotor 27 is in turn initiated by the initiator 21, which then provides the desired high order detonation of the main explosive charge.

This arrangement is feasible on account of the high energy and velocity characteristic of high-velocity projec tiles. The initiation of a given explosive configuration is dependent upon two parameters: energy applied and rate of application of the energy. The minimum energy and its rate of application levels required for detonation of high velocity projectiles are established by the specification for the ammunition.

The safety and rough handling tests establish the upper limit for impact energy and rate of application thereof, below which the initiator composition must not initiate. Finally, the impact parameters establish the limit for im pact energy and rate of application therefor, below which the initiator composition must function reliably. In highvelocity projectiles, the differences between these levels are of suificient magnitude to allow the design to comply with all three requirements.

The arming mechanism The description now proceeds to the arming mechanism. The firing train comprises the initiator material in the bore 18 (FIG. 1), a pellet 22 carried by the upper fuze body 23, a lead 24 carried by the ball rotor and other conventional firing train elements such as 25, carried by the ball rotor 27, and that disposed in bore 26 in the lower fuze body 11. When the fuze is armed these elements are in continuity: the initiator composition 21 followed by 18, 22, 24, 25 and 26. Before the ball rotor 27 is armed the axial channel containing elements 25 and 24 is angularly displaced with respect to the axis of this firing tr-ain (i.e., the spin axis of the fuze).

The upper fuze body 23 is generally cylindrical in form with a concavity opening out at its rear. The lower fuze body 11 has a generally similar circular concavity opening out at its front. The junction of these two concavities forms a journal in which the ball rotor 27 floats and is mounted. These bodies 23 and 11 constitute a split housing for the rotor.

At its front the upper fuze body 23 is screw threaded into the initiator housing 17 and this upper fuze body is formed with an annular flange at its rear about which extending portion 9 of the lower fuze body 11 is crimped (FIG. 1). Disposed in concentric relation to the lower fuze body is a safety ring 28 which is yieldably urged forwardly by a compression safety spring 29. This safety ring restrains in place a centrifugal spring 30 against which bear two safety pins 31 and 32 (FIG. 3) and the lower fuze body 11 is formed with ports 34 and 35 in which these pins are slidably mounted.

The rotor sphere is formed with depressions which accept for seating approximately one hemisphere each of driver bearings 36 and 37.

A cycle of operation of this fuze, preparatory to arming, is as follows: First, when the projectile is fired the setback force, operating on the ring 28, compresses spring 29 and the safety ring moves rearwardly permitting outthe initiator housing" '17. The initiator is positioned in" ward displacement of the centrifugal ring 30, the safety ring being formed in section to permit this displacement. Outward displacement of the centrifugal spring is caused by centrifugal force moving the safety pins 31 and 32 radially outwardly. This centrifugal force is due to the rotation of the projectile in the rifled barrel as the projectile moves through the barrel.

Second, the safety pins are finally displaced outwardly to the point where they release the rotor 27, the inner ends of the safety pins departing from the complementary locking depressions 34, 35 formed in the rotor sphere.

Third, it is emphasized at this point that the two driving balls or bearings 36 and 37 steer the rotor in a direction to align the elements 24'and 25 with the remainder'of the firing train and that the driving balls move along spirally contoured cam slots (FIG. 5

In the present invention the driving balls 3637 are utilized in steering the motion of the ball rotor 27. The present invention utilizes the cam surfaces 40, 41, 42 and 43 to develop the delay time. While prior art cams have been restricted to arrangements in which a cylindrical rotor is rotated about a shaft, with the detonator being aligned at a distance from the shaft, the present invention provides an arrangement of spherical rotor 27 and lead elements 24-25 which is in balance so far as its center of gravity is concerned, while the individual cross sections of the rotor are not symmetrical, referencing the axis of rotation. Arming begins when the fuze proper, specifically the split housing elements 11 and 23, begin to decelerate as far as the rotor 27 is concerned. The raceway formations within the split housing elements are such that, prior to its release the rotor does not move relative to the housing elements. For example, prior to such release the bearing 36 abuts against the shouldered end portions 45 of the raceway defined by 40 and 41 (FIG. 5), but when release of the rotor relative to the housing elements occurs then the spin of the projectile drives the rotor controlled by the bearings into the arming position. That is, the bearing 36 moves counterclockwise and rearwardly (FIG. 5) as far as the raceway 41 is concerned if viewed from the front of the projectile, i.e., toward aperture 47a, which is the complement of aperture 47b. It will be understood that the upper housing portion 23 is reversed as unassembled and as illustrated in FIG. 5. In assembly a bolt projects through 47a, 47b and another bolt through 48a, 48b. The raceway 40, 41 is such that the bearing 3-6 moves backwardly and counterclockwise (FIG. 5, main portion), while the bearing 37, not shown in FIG. 5, moves forwardly and counterclockwise, the raceway 42, 43 permitting this motion.

The bearings 36 and 37 tend, due to centrifugal force, to become as far removed as possible from the spin axis. While the raceways permit this motion at the same time as the split housing decelerates in spin, they at the same time constrain each of the bearings to move spirally, as Will be detailed below. Furthermore, when spinning, the rotor will tend to align itself in the position where the moment of inertia, referencing the axis of rotation, is a maximum.

Note the bearing 36 in FIG. 6. As the rotor goes toward and into the armed position the rotor twists counterclockwise as far as an observer looking along the spin axis ZZ into the nose of the projectile is concerned, a component of motion indicated by the angle theta, but as far as an observer looking along the axis YY in the direction of the arrow in FIG. 6 is concerned, the rotor also moves in a clockwise direction as far as the axis YY is concerned. The end result is that the rotor moves so as to place the bearings 36 and 37 along the XX axis, where they are at maximum distance from the spin axis ZZ.

It will be understood that the fuze as a whole spins at a counterclockwise direction from the point of view of one looking at its nose.

FIG. 6 is taken from the point of view of one at the front of the nose of the fuze, looking backward. The axis ZZ is the spin or central or longitudinal axis of the fuze.

A vertical plane passed through the central axis of the fuze and extending longitudinally along the fuze has an XX and the plane containing it is the X2 plane. The horizontal plane through the spin axis and including the YY axis is the YZ plane. The vertical plane transverse or normal to the other two planes, passing through the origin (i.e., center of rotor 27) and including the XX axis, is referred to as the XY plane. It will be observed that the spin axis ZZ is the fore and aft axis through the origin or center of the spherical rotor. The YY axis is the horizontal axis extending transversely or laterally through said origin. The XX axis is the vertical axis extending vertically through said origin.

As the fuze is armed the ball 36 moves rearwardly and counterclockwise as indicated by the line A (FIG. 6). That is, it moves relative to the YY axis and tries to get onto the XY plane. The reason for this is that centrifugal force, acting on the bearings, tends to cause the hearings to move as far away from the spin axis as possible, and furthermore, the rotor will tend to align itself in a position where its moment of inertia around the spin axis is a maximum. The action is aided by the cam action of the raceways. Now the raceways 40-41 and 42-43 are shaped to permit the hearings to move, under the above forces, toward and into the XZ plane; as the split housing decelerates the inertia of the rotor also tends to cause it to move counterclockwise relative to the housing.

Therefore a radial line drawn on the axis terminated by the bearings and between the origin and the bearing 36 sweeps through an angle phi as the bearing 36 moves away from the observer and toward the XY plane and it moves through an angle theta as the bearing moves to the left of the observer and toward the X2. plane. The actual motion of the bearing 36 is a spiral A, because said motion is a composite of both of the angular displacements mentioned above.

FlGS. l and 2 show the unarmed and armed positions of the rotor and bearings.

Referring now to FlG. 5, it shows the bearing fairly close to the armed position. In FIG. 5 the cover 23 of the ball raceway has been removed and the cover portion 23 is referred to as the minor part and the remainder of the structure as the main portion of the figure. When the fuze as a whole decelerates, bearing in mind that the fuze spins counterclockwise (looking down the barrel of the gun), then the inertia of the rotor assembly is such that the bearing 36 tends to move to the left in FIG. 5. It has already been demonstrated that centrifugal force tends to cause it to move upward and through an angle phi. That is, the bearing 36 moves rearwardly and angular-1y away from the position marked C and toward the position marked D. From the foregoing, it follows that the raceway dtl, 41 is so formed as to become progressively shallower and radially more displaced from the center as one moves from the C region toward the D region. Now the bearing 36 moves counterclockwise and to the rear, whereas the other bearing 37 moves counterclockwise and to the front. Therefore as the displacement is from C toward D in FIG. 5, the raceway 42, 43 is progressively deeper and radially outward.

The raceways are designed to develop the delay time. Prior art cam designs have been restricted to rotors in which a cylindrical rotor is rotated about one axis, or a shaft, with the detonator being aligned off center. The present invention moves the ball rotor about both the spin (Z2) and transverse (YY) axes until the detonator is aligned on center. The raceways 40, 41, 4-2 and 43 are therefore characterized as spiral and formed with a longitudinal pitch.

The centrifugal forces acting on the two drive balls 35, 37 and the rotor 27 is derived from the projectile linear velocity and the twist in the firing weapon. The fraction of this force that is transmitted to the rotor to act as a driving torque is determined by the contour of the race ways.

It should be noted that the geometric: and gravitational center of the firing train elements or lead carried by the rotor is, in accordance with the present invention, located at the geometric center of the rotor sphere, and it is so located whether the rotor is in the armed or unarmed position. In other words, the rotor is balanced at all times. In the unarmed position the rotor has a component of angular displacement phi, parallel to the XZ plane, relative the Y axis illustrated in FIG. 6. Additionally, it also has a component of angular displacement theta, parallel to the XY plane and with respect to the Z axis. It will be apparent from FIGS. 5 and 6 that as the rotor moves to the armed position ball 36 is moved through a counterclockwise angle theta as far as the first quadrant of the XY plane is concerned. It is also moved cloukwise through an angle phi as far as the second quadrant of the ZX plane is concerned. It effectively turns about both the spin (ZZ) and transverse (YY) axes.

A characteristic of the present invention worthy of attention is that the rotor is mounted in a split housing without a rigid axis. The only constraints on the rotor are those exercized by the bearings and initially the centrifugal lock 31, 32 and the only constraints on the bearings are those imposed by the cam surfaces or raceways and the combination of the raceways and the centrifugal force acting on the bearings causes the theoretical rotor axis defined by the lead 24, 7.5 to move from the unarmed position to the armed position at which it is in line with the spin axis.

The invention provides the combination of a spherical rotor 27 having formed therein a channel which defines a rotor axis, a split housing 11, 23 adapted to house said rotor but to permit relative motion of the rotor and defining a spin axis 22 about which the split housing spins said rotor axis being normally tilted with respect to the spin axis, diametrically opposed bearings 36 and 37 seated on the periphery of the rotor, said housing being formed with raceways 4t), 41 and 42, 43 individual to said bearings, one of the raceways 4t), 41 being spirally formed and extending rearwardly and radially outward in the direction of spin and the other of said raceways 42, 43 being spirally formed and extending forwardly and radially outward in the direction of spin, whereby upon angular deceleration of the housing the bearings are displaced by centrifugal force and guided by said raceways to turn the rotor to align the rotor axis with the spin axis.

The invention further provides in a fuze having a spin axis (ZZ), the combination of a spherical rotor 27:

A lead 24, 25 disposed in an axial channel in said rotor;

A housing 11, 23 providing a generally spherical chamber walled to provide a mounting in which the rotor floats;

Centrifugal-force responsive means 36, 37 carried by said rotor at the ends of a geometrical axis which is normal to said channel and normally angularly offset both longitudinally and laterally from a vertical reference line (XX) through the center of said rotor;

And raceway formations 40, 41 and 42, 43 on said housing which guide the centrifugal-force responsive means spirally as the rate of spin of the housing changes with respect to the rate of spin to the rotor and as centrifugal force drives the centrifugal-force responsive means radially outwardly into the vertical reference line, to align said axial channel with the spin axis.

While there has been shown and described what is at present considered to be the preferred embodiment of the invention, it will be understood by those skilled in the art that various changes and modifications may be made therein without departing from the scope of the invention as defined by the appended claims.

We claim:

1. In a fuze having a spin axis, the combination of:

a spherical rotor,

a lead disposed in an axial channel in said rotor,

a housing having a generally spherical chamber walled to provide a mounting in which the rotor floats,

centrifugal-force responsive means carried by said rotor at the ends of a geometrical axis which is normal to said channel and normally tilted both longitudinally and laterally by predetermined angles phi and theta, respectively, from a reference line XX through the center of said rotor, said geometrical axis being normally tilted out of the XY and XZ planes of an orthogonal framework of Cartesian coordinates,

and raceway groove formations on said housing which guide the centrifugal-force responsive means spirally and drive such means with longitudinal pitch as the rate of spin of the housing changes with respect to the rate of spin of the rotor, and as the centrifugalforce responsive means is driven toward the reference line to align said axial channel with the spin axis ZZ,

where XX is a reference line through the center of the rotor,

YY is a line normal to XX and ZZ,

and ZZ is the spin axis with which the channel is aligned as the centrifugal force-responsive means is driven.

2. The combination in accordance with claim 1 in which the centrifugal-force responsive means comprises bearings seated on the periphery of the rotor.

3. The combination in accordance with claim 2 in which the moment of inertia referred to the spin axis is maximized in the armed position of the rotor.

4. The combination in accordance with claim 2 in which the drive of the centrifugal-force responsive means occurs as the housing decelerates.

5. In a fuze, the combination of:

a spherical rotor having formed therein a channel which defines a rotor axis,

a split housing adapted to house said rotor but to permit relative motion of the rotor and defining a spin axis about which the split housing spins, said rotor axis being normally tilted both laterally and vertically with respect to the spin axis,

diametrically opposed bearings seated on the periphery of the rotor,

said housing being formed with raceways individual to said bearings,

one of the raceways being spirally formed and extending rearwardly and radially outward in the direction of spin and the other of said raceways being spirally formed and extending forwardly and radially outward in the direction of spin,

whereby upon deceleration of the housing the bearings are displaced by centrifugal force and guided and cammed by said raceways to turn the rotor to align the rotor axis with the spin axis.

6. The combination in accordance with claim 5,

and means comprising locking pins normally projecting into the rotor for locking the rotor in unarmed position, said locking means being responsive to cen trifugal force to free the rotor.

7. The combination in accordance with claim 6,

a retainer spring yieldable to permit displacement of said locking pins,

and means normally restraining said retainer spring but responsive to setback forces to release it.

8. The combination of:

a spherical rotor having formed therein a channel which defines a rotor axis,

a socket adapted to house said rotor but to permit rotation of the rotor relative to the socket and defining a central axis,

diametrically opposed bearings seated on the periphery of the rotor,

said socket being formed with raceways individual to said bearings,

one of the raceways being spirally formed and extending rearwardly and radially outward and the other of said raceways being spirally formed and extending forwardly and radially outward whereby upon angular displacement of the socket and rotor relative to each other the bearings are guided and cammed by said raceways to cause the rotor to change both the lateral and vertical tilt of the rotor axis relative to the central axis.

9. The combination of:

a spherical rotor having formed therein a channel which defines a rotor axis,

a split housing adapted to house said rotor but to permit relative motion of the rotor and defining a longitudinal axis,

diametrically opposed bearings seated on the periphery of the rot-or,

said housing being formed with raceways individual to said bearings,

one of the raceways being spirally formed with a longitudinal pitch and the other of said raceways being spirally formed with a longitudinal pitch in the direction opposite to the first mentioned pitch whereby upon deceleration of the housing the bearings are displaced by centrifugal force and guided and cammed by said raceways to cause the rotor to align the rotor axis with the spin axis.

10. In a fuze having a spin axis, the combination of:

a spherical rotor,

a lead disposed in an axial channel in said rotor,

a housing having a generally spherical chamber walled to provide a mounting in which the rotor floats, centrifugal-force responsive means carried by said rotor at the ends of a geometrical axis which is normal to said channel and normally tilted both longitudinally and laterally by predetermined angles phi and theta, respectively, from a reference line XX through the center of said rotor,

said geometrical axis being normally tilted out of the XY and X2 planes of an orthogonal framework of Cartesian coordinates,

raceway groove formations on said housing which guide the centrifugal-force responsive means spirally and drive such means with longitudinal pitch as the rate of spin of the housing changes with respect to the rate of spin of the rotor, and as the centrifugalforce responsive means is driven toward the reference line to align said axial channel with the spin axis ZZ, where XX is a reference line through the center of the rotor,

YY is a line normal to XX and ZZ, and

ZZ is the spin axis with which the channel is aligned as the centrifugal-force responsive means is driven,

an ogive secured to the housing,

an initiator disposed within said ogive, and comprising a mushroom shaped composition having a stern and a spreading portion formed to be truncated at its front and to be spaced from and geometrically to be similar to the interior wall of said ogive and to terminate rearwardly of said stem, said initiator further comprising a form-sustaining cover between the composition and the ogive, and

means comprising a former internally of the spreading portion and concentrically related to said stem portion for positioning the initiator within the ogive in such manner that the initiator is pinched either on graze or high angle impact.

11. In a fuze, an initiating device comprising, in combination:

an ogive having a generally conical interior wall,

an initiator comprising a mushroom shaped composition having a stem and a spread portion formed to be truncated at its front and to be spaced from and geometrically to be similar to the interior wall of said ogive and to terminate rearwardly of said stem,

a form-sustaining cover between the initiator and the ogive, and

a former internally of the spreading portion and concentrically disposed about the stem portion for positioning the initiator within the ogive in such manner 9 that the initiator is pinched either on graze 01' high 2,663,260 angle impact. 2,782,717 2,807,211 References Cited 3,190,222 UNITED STATES PATENTS r 2,364,643 12/1944 Moore et a1. 102-73 X 2,455,603 12/1948 Nichols 102-79 Thompson 102-79 Burri et a1 10279 X Podnos et a1 102-79 Holmstrom 10273 0 BENJAMIN A. BORCHELT, Primary Examiner.

G. H. GLANZMAN, Assistant Examiner. 

